Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

McKillop, Alexander; Young, Derek W.

doi:10.1080/00397917708050782

Cited by 18 publications

(9 citation statements)

References 5 publications

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“…The formation of this complex was assessed by Sužnjević and co-workers by titration of H 2 O 2 with HgCl 2 in basic solutions. However, if the reactions shown in the above scheme were the only processes occurring at the electrode, no effect of the addition of antioxidants on the oxidation wave could be observed, because the antioxidants do not react with the mercury ions in the absence of hydrogen peroxide, at least under the experimental conditions of polarographic and voltammetric experiments …”

Section: Resultsmentioning

confidence: 99%

“…However, if the reactions shown in the above scheme were the only processes occurring at the electrode, no effect of the addition of antioxidants on the oxidation wave could be observed, because the antioxidants do not react with the mercury ions in the absence of hydrogen peroxide, at least under the experimental conditions of polarographic and voltammetric experiments. 39 It could be claimed that antioxidants act by reacting with the dissociated hydrogen peroxide and thus decreasing the concentration of the complex, this producing a decrease in the polarographic limiting current (or in the DPV peak current) that can be related to the antioxidant activity. However, this implies that the antioxidant must react with H 2 O 2 in the solution.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

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Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Palma

Montoya

Arteaga

et al. 2014

J. Agric. Food Chem.

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The anodic oxidation of mercury in presence of hydrogen peroxide in DPV 8 (Differential Pulse Voltammetry) was used to determine the antioxidant (AO) character of 9 radical scavengers. Hydroperoxide radical is formed at the potentials of the oxidation peak on 10 mercury electrodes, such radical reacting with the antioxidants in different extension. The 11 parameter C 10 (antioxidant concentration at which the peak area decreases in a 10%) is used to 12 measure the scavenging activity of the individual antioxidants. To establish the scavenging 13 activity of antioxidant mixtures as a whole it was selected the parameter, µ 10 as the reverse 14 V 10 , being V 10 the volume necessary to decrease the peak area in DPV in a 10%. The higher

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Section: Resultsmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Palma

Montoya

Arteaga

et al. 2014

J. Agric. Food Chem.

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“…The interference caused by mercury may be due to the oxidation of phenolic OH group of TE as reported in the literature for other molecules having phenolic OH group. 39 Likewise, there was no interference observed from anions in the above signalling process of m-CPBA. The anions used were halides, sulphate, carbonate, acetate, nitrate and phosphate.…”

Section: Effect Of Interfering Ions On Fluorescence Signallingmentioning

confidence: 93%

Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent

2018

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Thioesculetin (TE) is a sulfur analogue of esculetin. The UV-Vis absorption maximum of TE at 470 nm shifted to 357 nm in the presence of oxidising agent such as m-chloroperoxy benzoic acid (m-CPBA). With gradual increase in the m-CPBA concentration, the absorption band at 470 nm decreases while the band at 357 nm increases. The same system shows gradual increase in the fluorescence signal at 463 nm in the presence of m-CPBA. The fluorescence signal was unaffected in the presence of common anions and metal cations. The mechanism for optical signalling was due to the conversion of weakly fluorescent TE to fluorescent esculetin through desulfurization reaction. 13 C-NMR shows strong evidence in support of the chemical conversion of TE to esculetin. TE may find applications to probe the redox environment in various chemical and biochemical processes.

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“…9 In this study, DC polarography was used to follow the reaction between AOs and Hg 2+ . The possibility of determining AO activity based on polarographic monitoring of cathodic current of Hg 2+ decrease observed upon addition of individual AOs was demonstrated ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Reduction of Hg²⁺by Individual Phenolics and Complex Samples and Its Application in Polarographic Antioxidant Assay

Sužnjević

Petrović

Pastor

et al. 2015

J. Electrochem. Soc.

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Direct current (DC) polarographic antioxidant (AO) HPMC assay based on the decrease of anodic limiting current of [Hg(O 2 H)(OH)] (HydroxoPerhydroxoMercury(II) Complex-HPMC), formed in alkaline solution of H 2 O 2 , at potential of mercury oxidation, occurring upon AO addition, was validated and widely used recently. Here, a novel DC polarographic assay, MRAP (Mercury Reduction Antioxidant Power), based on the decrease of Hg 2+ cathodic current with addition of AOs was applied. Percentage of this decrease was plotted versus the amount of various individual phenolics or the volume of medicinal plant extracts, and the slope obtained was used to express AO activity. A high correlation between MRAP and HPMC assays was found for individual compounds (r = 0.974) and real samples (r = 0.968). MRAP was shown to be effective in the determination of AO activity of both synthetic mixtures of individual AOs and real samples containing various AOs. Agreement between the decrease of Hg 2+ cathodic current and HPMC anodic current lead to the assumption that Hg 2+ reduction causes a decrease in concentration of Hg 2+ available for HMPC complex formation, i.e. its anodic current decrease. The validity of MRAP assay was also confirmed through good correlation with FRAP assay.Behavior of H 2 O 2 in alkaline solution, at the potential of mercury oxidation, was investigated using direct current (DC) polarography by Sužnjević et al. 1 Formation of HydroxoPerhydroxoMercury(II) complex (HPMC) with 1:1 stoichiometry between Hg 2+ and H 2 O 2, which was first observed by Kikuchi and Murayama, 2 was proved by amperometric titration of H 2 O 2 with HgCl 2 and vice versa in Clark and Lubs buffer, pH 9.8. 1 The H 2 O 2 concentration, temperature and pH dependence of HPMC anodic current were comprehensively analyzed. The current response to antioxidant (AO) presence was employed to determine AO activity. Development and optimization of a DC polarographic AO assay based on HMPC current decrease was reported, 1 as was its wide application 3-5 (and papers cited therein). The slope of the plot of percentage of HPMC anodic current decrease vs the amount of individual or volume of complex samples was used to express AO activity.The polarographic and differential pulse (DP) voltammetric oxidation of peroxide on mercury electrodes was further examined by Palma et al. 6 Electrooxidation of peroxide involving hydroperoxide radicals and superoxide anions able to react with various AOs was suggested. 6 Anodic oxidation of mercury in the presence of H 2 O 2 in DP voltammetry was used to determine the AO character of radical scavengers, based on the decrease of the area under the observed anodic current peak. 7 Concentration of individual AOs or volume of real samples at which the area decreased by 10%, as well as their reciprocal values, 7 were used for expressing scavenging activity against hydroperoxide radical, proposed to react with AOs.Although assays developed by Sužnjević et al. 1 and Palma et al. 7 were successfully applied to various individual an...

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Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

Cited by 18 publications

References 5 publications

Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent

Reduction of Hg²⁺by Individual Phenolics and Complex Samples and Its Application in Polarographic Antioxidant Assay

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Oxidation of Phenols and Hydroquinones by Mercury(II) Trifluoroacetate and Mercury(II) Oxide

Cited by 18 publications

References 5 publications

Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Determination of Antioxidant Activity of Spices and Their Active Principles by Differential Pulse Voltammetry

Colorimetric and fluorescence signalling of thioesculetin in presence of oxidising agent

Reduction of Hg2+by Individual Phenolics and Complex Samples and Its Application in Polarographic Antioxidant Assay

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Reduction of Hg²⁺by Individual Phenolics and Complex Samples and Its Application in Polarographic Antioxidant Assay